Device for separating components from a substrate, in particular for unsoldering electronic components

ABSTRACT

Disclosed is a device for separating components (3, 20), in particular electronic components which are connected to a support such as a circuit board (1) by a fixing material such as solder and can be lifted from the support with the aid of a gripping element (17) under a preloaded force acting in the direction in which the components (3, 20) are to be lifted from the support. A lifting device (13) connected to the gripping element (17) causes the preloaded force to become effective when the fixing material reaches its melting temperature. The lifting device (17) is provided with a retaining member (9, 25, 31, 33) whose melting temperature is equal to or higher than that of the fixing material and which triggers the action of lifting the component (3, 20) when the fusible material melts.

The invention relates to a device for separating components connected toa substrate by a fusible or meltable material from said substrate and,in particular, for unsoldering components, in particular electroniccomponents connected to a support, in particular a circuit board, by asolder. The device lifts the components from the support by means of agripping element under a preloaded force acting in the direction inwhich the components are to be lifted from the support, wherein alifting device connected to the gripping element causes the preloadedforce to become effective when the fixing material reaches its meltingtemperature.

A device of this kind is described in DE-A-42 11 241. In this device, agripping element or a bonding device is used as the lifting device beingpreloaded by a spring or another elastic means. The spring exerts atensile force on the component to be unsoldered causing the respectivecomponent to be lifted when the soldering joints by means of which thecomponent is connected to the circuit board have been caused to melt.Until that point of time the entire force of the spring acts on thatcomponent whose soldered terminals are subject to a respective load,thus possibly causing these soldering joints to rupture before theirsolder melts and leading to a destruction in the component and thecircuit board.

It is an object of the invention to overcome this risk. According to theinvention, this is achieved by providing the lifting device with aretaining member consisting of a meltable material, e.g. a fusionadhesive or a metal alloy similar to a solder, the melting temperatureof which is equal to or higher than the melting temperature of thefusible material or the solder, and which triggers the action of liftingthe component when the material or metal alloy melts.

Although in the following the invention is described in particular onthe basis of a device for unsoldering components connected to a supportby means of a metal alloy similar to a solder, the principle accordingto the invention can be used in all those cases in which the fixingmaterial, such as an adhesive, has a specific melting temperature and arespective material having an essentially equal or higher meltingtemperature is used for the retaining member.

If a metal alloy similar to a solder is used as the retaining member,its melting temperature can easily be adapted to the melting temperatureof the solder so that when the solder melts and releases the respectivecomponent immediately also the retaining member is caused to melt andthus triggers the lifting of the component. The preloaded force actingon the lifting device, which triggers a movement of the lifting deviceupon melting of the retaining element, thus becomes effective only afterthe solder melts so that the preloaded force can only have an effect onthe component when it had already been released from the support due tothe melting of the solder. Therefore, when the component is stillconnected to the support by the solid solder, the preloaded force doesnot act on the component. If a metal alloy similar to a solder which hasa melting temperature equal to the melting temperature of the solder isused for the retaining element, e.g. when the same material compositionis used, first also the solder melts and then the retaining elementmelts since the heating up necessary for the unsoldering process becomesfirst effective on the soldering joints of the components and, with aslight delay, in the same way on the retaining element since, due to itsconnection to the lifting device, it is surrounded by components whichfirst cause a certain heat absorption. If the melting temperature of themetal alloy similar to a solder is higher than that of the solder, whenheat is applied for unsoldering the components the solder meltsautomatically first and only then the retaining element melts if, ofcourse, the application of heat for the unsoldering process takes placesuch that in the area of the components and the lifting device atemperature is reached which is higher than the melting temperature ofthe solder and at least equal to the melting temperature of theretaining element. This is for example the case when a vapor phase isused for the unsoldering process as described in the above-mentionedDE-A-42 11 241.

In case the melting temperature of the metal alloy similar to a solderis higher than the melting temperature of the solder, it is appropriateto select the first melting temperature only slightly higher in order toprevent the components from being heated too much. Advantageously, themelting temperature of the metal alloy similar to a solder is a fewdegrees Celsius higher than the melting temperature of the solder.

There are different possibilities of how to form the retaining element.An advantageous possibility is to form the retaining element as asupporting member for the lifting device. In this case the liftingdevice is held by the supporting member and can thus not exert a tensileforce on the component until the retaining member has reached itsmelting temperature. When this melting temperature is reached, thesupporting member loses its effect so that the lifting device can liftthe component from the support. The supporting member is advantageouslyarranged in an open container from which it can easily be taken outafter melting and thus becoming a metal alloy part being ineffective inthis connection. This metal alloy part can either be thrown away or canbe used again by remelting. For unsoldering a further component,however, a non-deformed supporting element must be introduced into thecontainer as the retaining element.

The retaining element can also be formed as a thread clamped between thelifting device and a holding means. In this case, the thread holds thelifting device against the preloaded force until the thread melts;subsequently, the lifting device can lift the component from thesupport.

A further possibility for forming the retaining element is to form it asa block into which a tension rod linked with the lifting deviceimmerses. For connecting the block to the tension rod, the metal alloysimilar to a solder is first melted open and the tension rod is immersedinto the melt. Then the melt is allowed to cool to form the block whichthen holds the immersed tension rod and thus blocks the lifting deviceuntil the block melts. The tension rod can be pulled out of the moltenblock by the preloaded force by means of the movement of the liftingdevice, and the respective component is thus lifted.

A further possibility for forming the retaining element is to use itlike a shearing pin. The shearing pin, a known component, acts by beingpushed through truly-aligned holes of two components which are moved onepast the other and thereby preventing the movement of the components.Only when a force causing the shearing of the shearing pin is acting onthe components can the components be displaced against each other. Incase it is used as a retaining element, this means that it is pushedinto truly-aligned holes of two components which are moved one past theother, whilst, however, no shearing of the pin takes place, but themovability of the components is achieved when the pin is caused to melt.The components are on the one hand a part of the lifting device and, onthe other hand, a somehow rigidly connected part.

The molten material or the metal alloy similar to a solder of theretaining member can advantageously shift during melting, e.g. flowaway, so that by utilizing the gravitational force the lifting meansmoves such that the component is lifted from the support.

Springs causing the lifting movement need not be used in this case.However, within the invention it is also possible to additionally usesuch springs in support of the gravitational force.

The lifting device is advantageously formed as a lever on which thepreloaded force is acting and the one end of which is connected to thegripper spacedly linked with the retaining member. The lever can eitherbe a single or double lever.

The exemplifying embodiments of the invention are disclosed in theFigures in which

FIG. 1 shows the device with a double lever and a retaining elementformed as a supporting means in the position before lifting thecomponent;

FIG. 2 shows the same device with a molten supporting member and alifted component;

FIG. 3 shows a similar device with a single lever and a retainingelement formed as a thread;

FIG. 4 shows a device with a single lever and a retaining element formedas a block;

FIG. 5 shows a retaining element which is formed as a shearing pin;

FIG. 6 shows a device with flowing-off molten material; and

FIG. 7 shows a device with displaceable molten material.

FIG. 1 shows a circuit board 1 with components 2 and 3 soldered thereto,wherein the components 2 and 3 are components which can in any knownmanner be soldered to a circuit board, e.g. resistors, transistors,integrated circuits or chips, etc. Component 3 is a larger componentwhich can, e.g., be formed by an integrated circuit. As apparent,components 2 and 3 are connected to the circuit board 1 either planelyor via terminals extending therefrom.

The frame 4 is placed on the circuit board 1 by means of its posts 5 and6 such that the posts 5 and 6 directly contact free areas of the circuitboard 1. The frame 4 carries the container 7 having a hollow space 8enlarging conically towards the outside in which the retaining member 9is introduced. This retaining member supports the lever arm 10 of thedouble lever 11 which also comprises the second arm 12 hinged to thelifting device 13. The double lever 11 is arranged on the swiveling axis14 which can be arranged stationarily in any desired way, as shown inFIG. 1. However, it is of course possible to provide the swiveling axis14 on the frame 4. The pressure spring 15 is acting on the lever arm 12,the one end of the pressure spring being supported by the frame 4 andthe other end by the lever arm 12 thus providing the double lever 11with a preloaded force by means of which the lever arm 12 with thelifting device 13 is preloaded in the lifting direction indicated by thearrow next to the lifting device 13. The lifting device 13 is secured bythe disc 16 provided thereon against the lever arm 12 such that thelifting device 13 can be swiveled to a certain extent with respect tothe lever arm 12. The lifting plate 17 to which, in this case, thecomponent 3 is fixed, is provided on that end of the lifting device 13facing away from the disc 16. The lifting plate 17 thus acts as thegripper of a lifting device formed by the double lever 11. Of course,also further known embodiments can be used for forming this gripper,e.g. a magnet, a suction plate or also a gripper formed as tongs, etc.

In this case, the retaining member 9 is formed as a rod consisting of ametal alloy similar to a solder, the melting temperature of which beingsomewhat higher than the melting temperature of the solder (e.g. 190°and 185°), by means of which the components 2, 3 are soldered to thecircuit board 1 in a known manner. In the position shown in FIG. 1 theretaining member 9 receives the force of the pressure spring 15 so thatthe lifting device 13 cannot exert a tensile force on the component 3,i.e. the terminals 18 of the component 3 are not subject to a tensileload.

In order to unsolder the component 3, the arrangement shown in FIG. 1 isheated, i.e. in a vapor phase whose temperature is higher than themelting temperature of the solder connecting the terminals 18 to thecircuit board 1 and that of the retaining element 9. Due to the heatingthe solder holding the terminals 18 melts first thereby releasing thecomponent 3 from the circuit board 1. Upon heating up of the entirearrangement, also the retaining element 9 melts and thus collapses, andthe molten material is collected in the container 7, as shown in FIG. 2.In this process, the retaining element 9 collapses thus causing thecompressive force of the pressure spring 15 to become effective andturning the double lever in the position shown in FIG. 2. Via thelifting device 13 and the lifting plate 17, the lever arm 12 takes alongthe component 3 whose soldering joints had already been molten. In thisway, the component 3 is removed from the circuit board 1 without anystresses being able to appear between the component 3 with its terminals18 and the circuit board 1. After cooling down, the molten material ofthe retaining element 9 contained in the container 7 forms the cake 19which is either thrown away or reused for forming a new retainingelement.

In contrast to the embodiment according to FIGS. 1 and 2, the variantdisclosed in FIG. 3 shows the single lever 22 which is on one sidesupported by the swiveling axis 23. In principle, this supportcorresponds to that of the arrangement according to FIGS. 1 and 2. Theend of the lever 22 facing away from the swiveling axis 23 is, like inthe embodiment according to FIGS. 1 and 2, hinged to the lifting device13 to which the component 20 is bonded via the lifting plate 17. Also inthis case the component 20 is an integrated circuit which, however, issoldered to the circuit board by means of terminals 24 passed throughthe circuit board 1, namely on the side facing away from the component20. This kind of connection between component and circuit board is alsoknown. The further shown component 21 is also connected to the circuitboard 1 by means of terminals passed through the circuit board 1.

The pressure spring 15 is acting on the lever 22, the force of saidpressure spring being received by the thread or fiber 25 in the positionshown in FIG. 3. Like in the embodiment according to FIGS. 1 and 2, thisthread is again the retaining element consisting of a metal alloy, uponmelting of which the force of the spring 15 can become effective sincein this case the thread 25 disconnects the connection formed by it. Oneend of the thread 25 is connected to the retainer 27 by means of thescrew 26 connected to the lever 22, said screw being shown in principle.The other end of the thread 25 is correspondingly connected to theretainer 28 connected to the frame 4.

When the arrangement according to FIG. 3 is heated in a similar way asdescribed in connection with FIGS. 1 and 2, first the solder at theterminals 24 melts, thereby releasing the component 20. Then also thethread 25 melts and the compressive force of the pressure spring 15 canthus become effective and swivels the lever 22 about the axis 23. As isin principle apparent from FIG. 2, the component 20 is lifted from thecircuit board 1. In connection with the arrangement according to FIG. 3,this position is not shown; however, in this connection reference ismade to the statements made in connection with FIG. 2.

FIG. 4 is a modification of the arrangement according to FIG. 3, i.e.with respect to the fact that the compressive force of the spring 15 isreceived by the tension rod 29 linked with the lever 22. The tension rod29 is melted into the block 31 which, like in the above-mentionedembodiments, is made of a metal alloy similar to a solder. The container30 comprises the opening 32 converging towards the outside, whichprevents the solid block 31 from being pulled out of the container 30thereby also holding in place the tension rod 29. Like the container 7according to FIGS. 1 and 2, the container 30 is connected to the frame4.

When the arrangement shown in FIG. 4 is heated, the same effect resultsas in the arrangement according to FIG. 3, i.e. the rod 29 is releasedby melting the block 31 so that the compressive force of the pressurespring 15 can have an effect on the lever and can thus lift thecomponent 20, whose soldering joints had already been molten, from thecircuit board 1.

A further modification of the arrangements according to FIGS. 3 and 4 isshown in FIG. 5 in which the retaining element is formed like a shearingpin 33. The shearing pin 33 passes through the walls of the holder 34and a hole in the link 35 which is hinged to the lever 22 in a mannersimilar to that of the rod 29 according to FIG. 4. The shearing pin 33being the retaining element again consists of the metal alloy describedabove, which also melts after the solder for connecting the componentsmelts and thereby allows the link 35 to be pulled out of the retainer34. Thus, the compressive force of the pressure spring 15 can becomeeffective and can lift the component 20 from the circuit board asdescribed in connection with FIGS. 3 and 4.

In the embodiment schematically shown in FIGS. 6a and b, the devicecomprises a lever 42 arranged on a swiveling axis 44, at the one (theright one in the drawing) end 42b of which the fusible material 48 isprovided. The lifting device 43 is hinged between the swiveling axis 44and the fusible material 48. If the temperature increase is high enough,the material 48 melts and flows into the basin 49. If a suitablecounterweight of the left lever section 42a is selected, the lever 42 isswiveled according to FIG. 6b after the fixing material (e.g. solder)melts and the component 3 is lifted from the carrier 1.

If the temperature increase is great enough, in an embodiment accordingto FIG. 7 the melting material 58 flows on an e.g. channel-like lever 52(having a swiveling axis 54) from the higher end portion 52b to thelower end portion 52a. By means of this weight displacement the lever 52exerts a vertical tensile force on the component via the lifting device53, and when the fixing material of the component 3 is molten, saidcomponent is lifted from the support.

We claim:
 1. Device for separating components (3, 20), in particularelectronic components which are connected to a support, in particular acircuit board (1), by a fixing material and can be lifted from thesupport by means of a gripping element (17) under a preloaded forceacting in the direction in which the components (3, 20) can be liftedfrom the support, wherein a lifting device (13) connected to thegripping element (17) causes the preloaded force to become effectivewhen the fixing material reaches its melting temperature, characterizedin that the lifting device (17) is provided with a retaining member (9,25, 31, 33) made of a fusible material, whose melting temperature isequal to or higher than that of the fixing material and which triggersthe action of lifting the component (3, 20) when the fusible materialmelts.
 2. The device of claim 1, characterized in that said retainingmember is formed as a supporting member (9) for the lifting device (13).3. The device of claim 2, characterized in that said supporting member(9) is contained in an open container (7) from which the component madeof the fusible material and formed by the melting process can be lifted.4. The device of claim 1, characterized in that said retaining member isformed as a thread (25) clamped between said lifting device (22, 13) anda holding means (28).
 5. The device of claim 1, characterized in thatsaid retaining member is formed as a block (31) into which a tension rod(29) hinged to said lifting device (22) immerses.
 6. The device of claim1, characterized in that said retaining member is formed as a shearingpin (33).
 7. The device of claim 1, characterized in that by means oflocal displacement after melting and by using the gravitational forcesaid retaining member triggers a swiveling movement of the lever forlifting the component.
 8. The use of claim 7, characterized in that thefusible material (49) of said retaining member flows off when melting.9. The use of claim 7, characterized in that the fusible material (58)of said retaining member flows into a collecting basin (49) or along thelever (52).
 10. The device of claim 1, characterized in that saidlifting device is formed as a lever (11, 22), the preloaded force actingon said lever and the one end of said lever being connected with saidgripper (17) which is spacedly hinged to said retaining member (9, 25,31, 33).
 11. The use of claim 1, characterized in that a materialsimilar to a solder or a fusion adhesive is provided as the fusiblematerial of said retaining member.